Vascular disease, in particular cardiac infarction, is one of the most common fatal illnesses. It is caused by disease of the coronary arteries (arteriosclerosis), in which the build-up of deposits (arteriosclerotic plaque) causes occlusions in the coronary arteries.
Nowadays, if coronary angiography reveals serious stenoses in the coronary arteries, causing angina pectoris which restricts the patient's capability and/or puts the patient at risk, a PTCA (percutaneous transluminal coronary angioplasty) is carried out in the majority of cases. This is done by dilating the narrowings in the coronary arteries using a so-called “balloon catheter”.
The working mechanism of the conventional balloon angioplasty for lumen gain is based both on compression of the plaque and on the rearrangement of the non-compressible plaque constituents, facilitated by dissection of the inner and medial vascular layers, and on the excessive dilatation of the vessel circumference. The compression of large quantities of plaque may result in damage to the inner vascular wall, leading to an increased restenosis rate.
The restenosis rate can be reduced by using a stent in the dilated section of the vessel. Implantation of the stent prevents any modification in vessel structure due to the mechanical restoring force of the stent. A significant disadvantage of the method is the additional process stage and the additional costs for the stent.
The cutting balloon is a special balloon on which are mounted three or four small blades depending on the size of the balloon. These are directed upward when the balloon is inflated and make longitudinal incisions into the vascular deposits or “shave” plaque from the vascular wall, before the coronary artery is dilated by the balloon.
The object of this technique is to minimize or even eliminate the elastic restoring force, in order to achieve a wider vascular diameter following the dilatation. Furthermore, irregular lacerations in the inner vascular wall, which might cause acute obstructions following the balloon inflation procedure, are avoided. Clinical studies show that even hyperplasia (inflammatory response with swelling) of the inner layer following balloon dilatation, can also be reduced. Clinical studies have shown that the restenosis rate can be significantly reduced by using the “cutting balloon”.
A device according to the cutting balloon principle is described, for example, in WO 82/04388, “Coronary Cutting and Dilating Instrument” and in WO 02/078511 “Inflatable Medical Device with Combination Cutting Elements and Drug Delivery Conduits”. An example of a disclosed product is the Cutting Balloon Ultra from Boston Scientific, Mass., USA.
The interventions described above are implemented using an angiography device under x-ray monitoring by means of contrast media. The drawback of this method is that the coronary arteries are only shown in two dimensions and only the actual stenosis is shown on the x-ray image. During the intervention it is difficult for medical staff to distinguish between plaque and vascular wall. This increases the risk of incisions by the balloon blades being made in the wrong place, or of the incisions being too deep (resulting in “deep vessel wall injury”).
The problem is described inter alia in the paper “Impact of Deep Vessel Injury on Acute Response and Remodeling of Coronary Artery Segments After Cutting Balloon Angioplasty”, Mamoo Nakamura, The American Journal of Cardiology Vol. 91, Jan. 1, 2003.
The introduction of an IVUS (intravascular ultrasound) catheter into the vessel enhances the imaging information, yet has the disadvantage that a relatively expensive catheter must also be inserted into the patient and must be removed from the vessel before the balloon catheter is inserted. An IVUS system is described, for example, in EP 0 885 594 B1 and in U.S. Pat. No. 5,193,546.